Buoy array of magnetometers

ABSTRACT

A system includes a plurality of magnetometers that are each configured to generate a vector measurement of a magnetic field. The system also includes a central processing unit that is communicatively coupled to each of the magnetometers. The central processing unit is configured to receive from each of the plurality of magnetometers the respective vector measurement of the magnetic field. The central processing unit is further configured to compare each of the vector measurements to determine differences in the vector measurements and to determine, based on the differences in the vector measurements, that a magnetic object is near the plurality of magnetometers.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the priority of co-pending U.S.Application No. 62/343,842, filed May 31, 2016, of co-pending U.S.Application No. 62/343,839, filed May 31, 2016, and of co-pending U.S.Application No. 62/343,600, all of which are incorporated herein byreference in their entirety.

BACKGROUND

Various locating techniques use scalar measurements to determine thelocation of items. For example, radar can use triangulation to determinethe location of an object such as an airplane. However, scalarmeasurements are limited in their use because they include only amagnitude of measurement.

SUMMARY

An illustrative system includes a plurality of unmanned aerial systems(UASs) and a plurality of magnetometers each attached to a respectiveone of the UASs. Each of the magnetometers are configured to generate avector measurement of a magnetic field. The system also includes acentral processing unit in communication with each of the plurality ofmagnetometers. The central processing unit is configured to receive,from each of the plurality of magnetometers, a first set of vectormeasurements and corresponding locations. The corresponding locationsindicate where a respective magnetometer was when the respective vectormeasurement of the first set of vector measurements was taken. Thecentral processing unit is also configured to generate a magneticbaseline map using the first set of vector measurements and receive,from a first magnetometer of the plurality of magnetometers, a firstvector measurement and a first corresponding location. The centralprocessing unit is further configured to compare the first vectormeasurement with the magnetic baseline map using the first correspondinglocation to determine a first difference vector and determine that amagnetic object is in an area corresponding to the area of the magneticbaseline map based on the first difference vector.

An illustrative method includes receiving, from each of a plurality ofmagnetometers, a first set of vector measurements and correspondinglocations. Each of the magnetometers are attached to one of a pluralityof unmanned aerial systems (UASs). Each of the magnetometers areconfigured to generate a vector measurement of a magnetic field. Thecorresponding locations indicate where a respective magnetometer waswhen the respective vector measurement of the first set of vectormeasurements was taken. The method also includes generating a magneticbaseline map using the first set of vector measurements and receiving,from a first magnetometer of the plurality of magnetometers, a firstvector measurement and a first corresponding location. The methodfurther includes comparing the first vector measurement with themagnetic baseline map using the first corresponding location todetermine a first difference vector. The method also includesdetermining that a magnetic object is in an area corresponding to thearea of the magnetic baseline map based on the first difference vector.

An illustrative system includes a plurality of magnetometers that areeach configured to generate a vector measurement of a magnetic field.The system also includes a central processing unit that iscommunicatively coupled to each of the magnetometers. The centralprocessing unit is configured to receive from each of the plurality ofmagnetometers the respective vector measurement of the magnetic field.The central processing unit is further configured to compare each of thevector measurements to determine differences in the vector measurementsand to determine, based on the differences in the vector measurements,that a magnetic object is near the plurality of magnetometers.

An illustrative method includes receiving, from each of a plurality ofmagnetometers, a respective vector measurement of a magnetic field. Themethod also includes comparing each of the vector measurements todetermine differences in the vector measurements. The method furtherincludes determining, based on the differences in the vectormeasurements, that a magnetic object is near the plurality ofmagnetometers.

An illustrative system includes a first magnetometer configured todetect a first vector measurement of a magnetic field. The magneticfield is generated by a magnetic device. The system also includes asecond magnetometer configured to detect a second vector measurement ofthe magnetic field. The first magnetometer and the second magnetometerare spaced apart from one another. The system further includes aprocessor in communication with the first magnetometer and the secondmagnetometer. The processor is configured to determine a location of themagnetic device in a three-dimensional space based on the first vectormeasurement and the second vector measurement.

The foregoing summary is illustrative only and is not intended to be inany way limiting. In addition to the illustrative aspects, embodiments,and features described above, further aspects, embodiments, and featureswill become apparent by reference to the following drawings and thedetailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are graphs illustrating the frequency response of a DNVsensor in accordance with some illustrative embodiments.

FIG. 2A is a diagram of NV center spin states in accordance with someillustrative embodiments.

FIG. 2B is a graph illustrating the frequency response of a DNV sensorin response to a changed magnetic field in accordance with someillustrative embodiments.

FIGS. 3A and 3B are diagrams of a buoy-based DNV sensor array inaccordance with some illustrative embodiments.

FIG. 4 is a flow chart of a method for monitoring for magnetic objectsin accordance with some illustrative embodiments.

FIG. 5 is a diagram of a buoy-based DNV sensor array in accordance withsome illustrative embodiments.

FIG. 6 is a diagram of an aerial DNV sensor array in accordance withsome illustrative embodiments.

FIG. 7 is a flow chart of a method for monitoring for magnetic objectsin accordance with some illustrative embodiments.

FIG. 8 is a block diagram of a computing device in accordance with someillustrative embodiments.

The foregoing and other features will become apparent from the followingdescription and appended claims, taken in conjunction with theaccompanying drawings. Understanding that these drawings depict onlyseveral embodiments and are, therefore, not to be considered limiting ofscope of the disclosure, which will be described with additionalspecificity and detail through use of the accompanying description.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings, which form a part hereof. In the drawings,similar symbols typically identify similar components, unless contextdictates otherwise. The illustrative embodiments described in thedetailed description, drawings, and claims are not meant to be limiting.Other embodiments may be utilized, and other changes may be made,without departing from the spirit or scope of the subject matterpresented here. It will be readily understood that the aspects, asgenerally described herein, and illustrated in the figures, can bearranged, substituted, combined, and designed in a wide variety ofdifferent configurations, all of which are explicitly contemplated andmake part of this disclosure.

In various embodiments described herein, an array of magnetometers maybe used to locate a magnetic object, such as a ferromagnetic orparamagnetic object. Multiple magnetometers are distributed across anarea, which can be a two-dimensional area (e.g., the surface of a bodyof water) or a three-dimensional area (e.g., along a water column orattached to unmanned aerial vehicles). The magnetometers are sensitiveenough to detect relatively small changes in the sensed earth's magneticfield. Differences in the sensed earth's magnetic field from each of themagnetometers can be used to detect and determine the location of anobject that interferes with the earth's magnetic field.

For example, multiple unmanned aerial systems (UASs) such as flyingdrones are each fitted with a magnetometer. The UASs fly around an areathat may be monitored. Each of the magnetometers sense a vectormeasurement of the earth's magnetic field at the same time. The earth'smagnetic field is the same (or substantially the same) for all of theUASs. Objects can alter the earth's magnetic field as sensed by theUASs. For example, vehicles such as cars, trucks, tanks, etc. that aremade primarily of steel or other paramagnetic material deflect or alterthe earth's magnetic field.

The UASs fly around the monitored area and take simultaneousmeasurements of the earth's magnetic field. Each of the measurements maybe a vector measurement that includes a strength and direction of theearth's magnetic field. If the vehicle does not move over time, theearth's magnetic field detected by each of the UASs does not change overtime at specific locations. If the vehicle moves, the vehicle's effecton the earth's magnetic field that is sensed by the UASs changes. Thesensed change in the earth's magnetic field can be used to determine thelocation of the vehicle over time.

For example, each of the UASs sense the earth's magnetic fieldsimultaneously. The simultaneous measurements can be compared to oneanother to determine anomalies or changes in the earth's magnetic fieldcaused by a magnetic object. For example, if there is no magnetic objectin the area that is being monitored, each of the UASs' sensed magneticfields may be the same. That is, there is no object within the monitoredarea that may be altering or moving the earth's magnetic field. But, ifthere is a magnetic object that is within the monitored area, theearth's magnetic field sensed by each of the UASs will be slightlydifferent depending upon the relative location of the magnetic object.For example, the vector measurement of a UAS that is close to themagnetic object will be different than the vector measurement of UASsthat are relatively far away from the magnetic object. The difference inthe vector measurements can be used to determine, for example, that themagnetic object exists and may be proximate to the UAS with the vectormeasurement that may be different than the other vector measurements.

In some such examples, once it is determined that the magnetic objectexists and may be relatively close to a particular UAS, the fleet ofUASs can be directed to the area of the magnetic object. Subsequentmeasurements can be taken to determine the location, size, shape, etc.of the magnetic object based on the sensed magnetic vectors and thelocation of the UASs. The UASs may be autonomous or may be controlledremotely.

In some embodiments described herein, the “magnetic object” may be aparamagnetic or a ferromagnetic object. In an alternative embodiment,the “magnetic object” may be (or include) an electromagnet. In otheralternative embodiments, the “magnetic object” may be any object thatalters the earth's magnetic field. For example, the “magnetic object”may be an object made of (or that includes) a material that alters theflux lines of the earth's magnetic field, but is not necessarilyparamagnetic, ferromagnetic, or electromagnetic. In such an example, thematerial may not be magnetic, but may still alter the flux lines of theearth's magnetic field.

A diamond with a nitrogen vacancy (DNV) can be used to measure amagnetic field. DNV sensors generally have a quick response to magneticfields, consume little power, and are accurate. Diamonds can bemanufactured with nitrogen vacancy (NV) centers in the lattice structureof the diamond. When the NV centers are excited by light, for examplegreen light, and microwave radiation, the NV centers emit light of adifferent frequency than the excitation light. For example, green lightcan be used to excite the NV centers, and red light can be emitted fromthe NV centers. When a magnetic field is applied to the NV centers, thefrequency of the light emitted from the NV centers changes.Additionally, when the magnetic field is applied to the NV centers, thefrequency of the microwaves at which the NV centers are excited changes.Thus, by shining a green light (or any other suitable color) through aDNV and monitoring the light emitted from the DNV and the frequencies ofmicrowave radiation that excite the NV centers, a magnetic field can bemonitored.

NV centers in a diamond are oriented in one of four spin states. Eachspin state can be in a positive direction or a negative direction. TheNV centers of one spin state do not respond the same to a magnetic fieldas the NV centers of another spin state. A magnetic field vector has amagnitude and a direction. Depending upon the direction of the magneticfield at the diamond (and the NV centers), some of the NV centers willbe excited by the magnetic field more than others based on the spinstate of the NV centers.

FIGS. 1A and 1B are graphs illustrating the frequency response of a DNVsensor in accordance with some illustrative embodiments. FIGS. 1A and 1Bare meant to be illustrative only and not meant to be limiting. FIGS. 1Aand 1B plot the frequency of the microwaves applied to a DNV sensor onthe x-axis versus the amount of light of a particular frequency (e.g.,red) emitted from the diamond. FIG. 1A is the frequency response of theDNV sensor with no magnetic field applied to the diamond, and FIG. 1B isthe frequency response of the DNV sensor with a seventy gauss (G)magnetic field applied to the diamond.

As shown in FIG. 1A, when no magnetic field is applied to the DNVsensor, there are two notches in the frequency response. With nomagnetic field applied to the DNV sensor, the spin states are notresolvable. That is, with no magnetic field, the NV centers with variousspin states are equally excited and emit light of the same frequency.The two notches shown in FIG. 1A are the result of the positive andnegative spin directions. The frequency of the two notches is the axialzero field splitting parameter.

When a magnetic field is applied to the DNV sensor, the spin statesbecome resolvable in the frequency response. Depending upon theexcitation by the magnetic field of NV centers of a particular spinstate, the notches corresponding to the positive and negative directionsseparate on the frequency response graph. As shown in FIG. 1B, when amagnetic field is applied to the DNV sensor, eight notches appear on thegraph. The eight notches are four pairs of corresponding notches. Foreach pair of notches, one notch corresponds to a positive spin state andone notch corresponds to a negative spin state. Each pair of notchescorresponds to one of the four spin states of the NV centers. The amountby which the pairs of notches deviate from the axial zero fieldsplitting parameter may be dependent upon how strongly the magneticfield excites the NV centers of the corresponding spin states.

As mentioned above, the magnetic field at a point can be characterizedby a vector with a magnitude and a direction. By varying the magnitudeof the magnetic field, all of the NV centers will be similarly affected.Using the graph of FIG. 1A as an example, the ratio of the distance from2.87 GHz of one pair to another will remain the same when the magnitudeof the magnetic field may be altered. As the magnitude is increased,each of the notch pairs will move away from 2.87 GHz at a constant rate,although each pair will move at a different rate than the other pairs.

When the direction of the magnetic field is altered, however, the pairsof notches do not move in a similar manner to one another. FIG. 2A is adiagram of NV center spin states in accordance with an illustrativeembodiment. FIG. 2A conceptually illustrates the four spin states of theNV centers. The spin states are labeled NV A, NV B, NV C, and NV D.Vector 201 is a representation of a first magnetic field vector withrespect to the spin states, and Vector 202 is a representation of asecond magnetic field vector with respect to the spin states. Vector 201and vector 202 have the same magnitude, but differ in direction.Accordingly, based on the change in direction, the various spin stateswill be affected differently depending upon the direction of the spinstates.

FIG. 2B is a graph illustrating the frequency response of a DNV sensorin response to a changed magnetic field in accordance with someillustrative embodiments. The frequency response graph illustrates thefrequency response of the DNV sensor from the magnetic fieldcorresponding to vector 201 and to vector 202. As shown in FIG. 2B, thenotches corresponding to the NV A and NV D spin states moved closer tothe axial zero field splitting parameter from vector 201 to vector 202,the negative (e.g., lower frequency notch) notch of the NV C spin statemoved away from the axial zero field splitting parameter, the positive(e.g., high frequency notch) of the NV C spin state stayed essentiallythe same, and the notches corresponding to the NV B spin state increasedin frequency (e.g., moved to the right in the graph). Thus, bymonitoring the changes in frequency response of the notches, the DNVsensor can determine the direction of the magnetic field.

Although specific mentions to DNV sensors are made, any other suitablemagnetometer may be used. For example, any suitable DNV sensor that candetermine the magnitude and angle of a magnetic field can be used. In anillustrative embodiment, a sensor that functions as described above maybe used, even if the diamond material is replaced with a differentmagneto-optical defect center material. Furthermore, although nitrogenvacancies are described herein, any other suitable vacancy or defect maybe used that functions in a similar manner. In yet other embodiments,any other suitable type of magnetometer that determines a magnitude anddirection of a magnetic field can be used, even if such a magnetometerdoes not include a magneto-optical defect center material. That is, thevarious embodiments and/or techniques described herein need not belimited to a particular style or type of magnetometer and can use anysuitable phenomena, physical characteristics, or mathematicalprincipals. Although references to DNV sensors are made herein, the DNVsensors may be replaced with any other suitable type of magnetometer.

FIGS. 3A and 3B are diagrams of a buoy-based DNV sensor array inaccordance with some illustrative embodiments. The system 300 includes abuoy 305, DNV sensors 310, a tether 315, and an anchor 320 in water 345.In FIG. 3A, there is no magnetic object 325 and the earth's magneticflux lines 330 are relatively straight. In FIG. 3B, the magnetic object325 causes a disturbance in the earth's magnetic field and causes achange in the earth's magnetic flux lines 330 as compared to the earth'smagnetic flux lines of FIG. 3A. In alternative embodiments, additional,fewer, and/or different elements may be used. For example, theembodiments shown in FIGS. 3A and 3B each show three DNV sensors 310,but in alternative embodiments, more or less than three DNV sensor 310may be used. Further, in alternative embodiments, each object labeled310 in FIG. 3A may include more than one DNV sensor. For example, eachobject labeled 310 may include two, three, four, etc. DNV sensors.

In the system 300 of FIG. 3A, the DNV sensors 310 are attached to thebuoy 305 via the tether 315. The buoy 305 floats at the surface of thewater 345. In alternative embodiments, the buoy 305 can have anysuitable density and may be suspended in the water 345. For example, thebuoy 305 may be suspended slightly below the surface of the water 345.In some embodiments, the buoy 305 may include a propulsion system thatcan cause the buoy 305 to be moved through the water 345.

In some embodiments, the system 300 can include an inertial compensationsystem. For example, the inertial compensation system can be anelectronic and/or software component that accounts for movement of theDNV sensors 310 and/or the buoy 305. For example, as the buoy 305 movesup and down or side to side with the waves of the water 345, theinertial compensation system can account for such movements. Forexample, in some embodiments, the DNV sensors 310 may not always beequally spaced apart, but may move with respect to one another dependingupon the movement of the buoy 305. Any suitable inertial compensationsystem can be used. For example, an inertial compensation system may beimplemented as software running on one or more processors of the buoy305.

The DNV sensors 310 hang from the buoy 305 via the tether 315. The DNVsensors 310 are distributed along the tether 315 such that the DNVsensors 310 are at different depths. The anchor 320 may be attached atthe end of the tether 315. In an illustrative embodiment, the anchor 320sits on or is embedded in the floor of the body of water 345 (e.g., thebottom of the sea or ocean). For example, the anchor 320 can anchor thebuoy 305 such that the buoy 305 may be relatively stationary and doesnot float away. In an alternative embodiment, the anchor 320 can hangfrom the buoy 305. In such an embodiment, the anchor 320 can be used tokeep the tether 315 taut. In an alternative embodiment, the anchor 320may not be used. For example, the tether 315 may be a rod.

In an illustrative embodiment, the buoy 305 includes electronics. Forexample, the buoy 305 can include a processor in communication with theDNV sensors 310. The buoy 305 can include a location sensor (e.g., aglobal positioning system (GPS) sensor). In an illustrative embodiment,the buoy 305 communicates wirelessly with a base station or remoteserver. For example, satellite communications can be used by the buoy305 to communicate with external devices.

In an illustrative embodiment, the DNV sensors 310 communicate with thebuoy 305 via the tether 315. For example, the tether 315 can include oneor more communication wires with which the DNV sensors 310 communicatewith the buoy 305. In alternative embodiments, any suitable method ofcommunication can be used, such as wireless communication or fiberoptics.

In an illustrative embodiment, the buoy 305 and the DNV sensors 310 arerelatively stationary over time. That is, the anchor 320 keeps thetether 315 taut and the DNV sensors 310 are fixed to the tether 315 suchthat constant distances are maintained between the buoy 305 and the DNVsensors 310. In some embodiments, the buoy 305 and the DNV sensors 310move up and down with respect to the earth along with the level of thewater 345, such as with tides, waves, etc. In alternative embodiments,the anchor 320 rests on the floor of the body of water 345, and the buoy305 keeps the tether 315 taught because the buoy 305 is buoyant. In suchembodiments, the buoy 305 may move with respect to the earth withmovement of the water 345 caused, for example, tidal movements,currents, etc. In most embodiments, however, the buoy 305 and the DNVsensors 310 are not subject to sudden movements. As noted above, in someembodiments, an inertial compensation system can be used to compensatefor movement of the DNV sensors 310 and/or the buoy 305. For example,the DNV sensors 310 may not always be aligned together. That is, some ofthe DNV sensors 310 may be tilted. In such an example, the inertialcompensation system can adjust the measurements (e.g., the directionalcomponent of the vector measurement) to account for the tilt of the DNVsensors 310 such that the adjusted measurements are as if all of the DNVsensors 310 were aligned when the measurements were taken. In suchembodiments, the DNV sensors 310 can include sensors that measure theorientation of the DNV sensors 310 (e.g., accelerometers).

Each of the DNV sensors 310 can be configured to take measurements of amagnetic field. For example, each of the DNV sensors 310 determine avector measurement of the earth's magnetic field. The DNV sensors 310take simultaneous measurements of the earth's magnetic field. The DNVsensors 310 can transmit the measured magnetic field to the buoy 305. Inan illustrative embodiment, the buoy 305 compares the measurements fromeach of the DNV sensors 310. If the measurements are the same (orsubstantially the same), then the buoy 305 can determine that there isnot a magnetic object nearby. If there is a difference that is above athreshold amount in either the direction or the magnitude of the sensedmagnetic field, the buoy 305 can determine that there is a magneticobject nearby. In an alternative embodiment, the buoy 305 does not makesuch determinations, but transmits the measurements to a remotecomputing device that makes the determinations.

FIGS. 3A and 3B show the system 300 with and without a nearby magneticobject 325. The magnetic object 325 can be any suitable paramagnetic orferromagnetic object such as a ship, a boat, a submarine, a drone, anairplane, a torpedo, a missile, etc. The magnetic flux lines 330 are thedashed lines of FIGS. 3A and 3B and are meant to a magnetic field forexplanatory purposes. The magnetic flux lines 330 are meant to beillustrative and explanatory only and not meant to be limiting. In anillustrative embodiment, the magnetic flux lines 330 are representativeof the earth's magnetic field. In an alternative embodiment, anysuitable source of a magnetic field can be used other than the earth,such as an electromagnet, a permanent magnet, etc.

As shown in FIG. 3A, without the magnetic object 325, the magnetic fluxlines 330 are straight and parallel. Thus, the angle of the magneticflux lines 330 through each of the DNV sensors 310 may be the same.Accordingly, when the angles of the magnetic field sensed by each of theDNV sensors 310 are compared to one another, the angles will be the sameand the buoy 305 can determine that there may be not a magnetic object(e.g., the magnetic object 325) nearby.

However, when a magnetic object 325 is nearby, as in the embodimentshown in FIG. 3B, the magnetic flux lines 330 can be disturbed and/orotherwise affected. The magnetic flux lines 330 of FIG. 3B do not passthrough the DNV sensors 310 at the same angle. Rather, depending uponhow far away from the buoy 305 that the DNV sensors 310 are, the angleof the magnetic flux lines 330 changes. Put another way, the angle ofthe magnetic field corresponding to the magnetic flux lines 330 may benot the same along the length of the tether 315. Thus, the sensedmagnetic field angle by each of the DNV sensors 310 are not the same.Based on the difference in the magnetic field angle from the DNV sensors310, the buoy 305 can determine that the magnetic object 325 may benearby.

Similarly, the strength of the earth's magnetic field can be used todetermine whether a magnetic object may be nearby. In the embodiment ofFIG. 3A in which there is no magnetic object 325, the density of themagnetic field lines 330 may be consistent along the length of thetether 315. Thus, the magnitude of the magnetic field sensed by each ofthe DNV sensors 310 may be the same. However, when the magnetic object325 disrupts the magnetic field, the density of the magnetic flux lines330 along the tether 315 (e.g., at the multiple DNV sensors 310) may benot the same. Thus, the magnitude of the magnetic field sensed by eachof the DNV sensors 310 may be not the same. Based on the differences inmagnitude, the buoy 305 can determine that the magnetic object 325 maybe nearby.

In an illustrative embodiment, the differences between the sensedmagnetic field at each of the DNV sensors 310 can be used to determinethe location and/or size of the magnetic object 325. For example, alarger magnetic object 325 will create larger differences in themagnetic field along the tether 315 (e.g., angle and magnitude) than asmaller magnetic object 325. Similarly, a magnetic object 325 that iscloser to the tether 315 and the DNV sensors 310 will create largerdifferences than the same magnetic object 325 that may be further away.

In an illustrative embodiment, the DNV sensors 310 make multiplemeasurements over time. For example, each DNV sensor 310 can take asample once per minute, once per second, once per millisecond, etc. TheDNV sensors 310 can take their measurements simultaneously. In someinstances, the magnitude and/or the direction of the earth's magneticfield can change over time. However, if each of the DNV sensors 310sense the earth's magnetic field at the same time, the changes in theearth's magnetic field are negated. Changes in the earth's magneticfield (e.g., a background magnetic field) can be caused, for example, bysolar flares. Thus, all of the DNV sensors 325 are affected the same bychanges in the earth's magnetic field/the background magnetic field.

For example, the DNV sensors 310 each simultaneously take a firstmeasurement of the earth's magnetic field. The buoy 305 can compare thefirst measurements of each of the DNV sensors 310 to determine if theremay be a magnetic object 325 nearby. The earth's magnetic field canchange and, subsequently, the DNV sensors 310 each simultaneously take asecond measurement of the earth's magnetic field. The buoy 305 cancompare the second measurements of each of the DNV sensors 310 todetermine if there may be a magnetic object 325 nearby. In both thefirst and second measurement sets, the buoy 305 compares the respectivemeasurements to each other. Thus, if there is a change in the earth'smagnetic field, the system 300 is unaffected because each of the DNVsensors 310 sense the same changes. That is, if there is no magneticobject 325 nearby, then subtracting the measurement of one DNV sensor310 from another is zero. This is true regardless of the strength ordirection of the earth's magnetic field. Thus, the system 300 isunaffected if the earth's magnetic field changes from one measurementset to another.

In an illustrative embodiment, the buoy 305 includes one or morecomputer processors that use electrical power. The buoy 305 can includea battery to power various components such as the processors. In anillustrative embodiment, the battery of the buoy 305 powers the DNVsensors 310. In some embodiments, the buoy 305 can include one or morepower generation systems for providing power to one or more of thevarious components of the system 300 such as the processors, thebattery, the DNV sensors 310, etc. For example, the buoy 305 can includea solar panel, a tidal generator, or any other suitable power generationsystem.

In an illustrative embodiment, the buoy 305 includes a GPS sensor todetermine the location of the buoy 305. The buoy 305 can transmitinformation such as the location of the buoy 305, an indication ofwhether a magnetic object may be nearby and/or where the magnetic objectis, the measurements from the DNV sensors 310, etc. to a remote stationvia radio transmissions. The radio transmissions can be transmitted to asatellite, a base station, etc. via one or more antennas.

Although FIGS. 3A and 3B illustrate the buoy 305 and the DNV sensors 310in water 345, alternative embodiments may include the buoy 305 and theDNV sensors 310 in any suitable substance. For example the, buoy 305 maybe a balloon such as a weather balloon and the DNV sensors 310 may besuspended in the air. In another embodiment, the buoy 305 may be placedterrestrially and the DNV sensors 310 can be located underground. Insome embodiments, the system 300 may be free-floating in space todetect, for example, satellites.

FIG. 4 is a flow chart of a method for monitoring for magnetic objectsin accordance with some illustrative embodiments. In alternativeembodiments, additional, fewer, and/or different elements may be used.Also, the used of a flow chart and/or arrows is not meant to be limitingwith respect to the order of operations or flow of information. Forexample, in some embodiments, two or more operations may be performedsimultaneously.

In an operation 405, measurements from magnetometers are received. Forexample, the buoy 305 can receive vector magnetic measurements taken bythe DNV sensors 310. In some illustrative embodiments, the measurementsare received simultaneously form multiple magnetometers. In somealternative embodiments, the magnetometers take simultaneousmeasurements, but the buoy 305 receives the measurements sequentially.

In an operation 410, the received measurements are compared. In someillustrative embodiments, the buoy subtracts a first measurement from asecond measurement that were received in the operation 405. Inembodiments in which more than two measurements are received in theoperation 405, an arbitrary one of the measurements is used as areference measurement, and the other measurements are compared to thereference measurement. In some alternative embodiments, all of themeasurements are compared to all of the other measurements.

In an operation 415, it is determined whether the differences betweenthe measurements are greater than a threshold amount. In someillustrative embodiments, each of the differences determined in theoperation 415 are compared to a threshold amount. In embodiments inwhich the measurements are vector measurements, the differences in theangle are compared to an angle threshold amount, and the differences inthe magnitude are compared to a magnitude threshold amount.

In some illustrative embodiments, if any of the differences are greaterthan the threshold amount, then the operation 415 determination is“yes.” In some alternative embodiments, the determination of theoperation 415 is “yes” if enough of the differences are above thethreshold amount. For example, if more than 25% of the differences aregreater than the threshold amount, then the determination of theoperation 415 is “yes.” In other embodiments, any suitable amount ofdifferences can be used, such as 50%, 75%, etc.

If the determination of the operation 415 is not “yes,” then in anoperation 420, it is determined that there may not be a magnetic objectnearby. The method 400 proceeds to the operation 405. If thedetermination of the operation 415 is “yes,” then in an operation 425,it may be determined that a magnetic object (e.g., the magnetic object325) is nearby.

In an operation 430, the size and/or location of the nearby magneticobject may be determined. For example, based on the differences in theangle and/or the magnitude of the measurements are used to determine thesize and location of the magnetic object 325. In an illustrativeembodiment, the determined differences are compared to a database ofpreviously-determined magnetic objects. For example, magnetic objects ofvarious sizes and at various distances can be measured by a system suchas the system 300. The differences in the magnetometer measurements canbe stored in connection with the size and location of the magneticobject. The differences determined in the operation 410 can be comparedto the differences stored in the database to determine which size andlocation most closely matches with the differences stored in thedatabase. In such an example, the size and location corresponding to theclosest match may be determined to be the size and location of themagnetic object in the operation 430. In an illustrative embodiment, thedatabase may be stored locally or may be stored remotely.

In embodiments in which the database may be stored remotely, thedifferences determined in the operation 410 can be transmitted to aremote computing device that can perform the operation 430. In anillustrative embodiment, the determination made in the operations 420,425, and/or 430 are transmitted to a remote computing device (e.g.,wirelessly). As shown in FIG. 4, the method 400 proceeds to theoperation 405.

FIG. 5 is a diagram of a buoy-based DNV sensor array in accordance withsome illustrative embodiments. The system 500 includes a buoy 505, DNVsensors 510, tethers 515, and a magnetic object 525. In alternativeembodiments, additional, fewer, and/or different elements may be used.For example, although FIG. 5 illustrates an embodiment with three DNVsensors 510, any suitable number of DNV sensors 510 can be used such astwo, four, five, ten, twenty, a hundred, etc. DNV sensors 510 can beused.

In some illustrative embodiments, the buoy 505 is similar to or the sameas the buoy 305. The DNV sensors 510 are connected to the buoy 505 viathe tethers 515. In some illustrative embodiments, the DNV sensors 510communicate with the buoy 505 via their respective tethers 515. Inalternative embodiments, the tethers 515 may not be used, and the DNVsensors 510 can communicate with the buoy via wireless communications.

In the embodiments shown in FIG. 5, the buoy 505 and the DNV sensors 510float on the water 545. In alternative embodiments, any suitablearrangement may be used. For example, the buoy 505 and/or the DNVsensors 510 may sink to the floor of the body of water 545 (e.g., thesea floor). In alternative embodiments, the buoy 505 and/or the DNVsensors 510 may be suspended in the water 545. For example, the buoy 505may float at the surface of the water 545, some of the DNV sensors 510float on the surface of the water 545, and some of the DNV sensors 510may be suspended within the column of water 545.

In an illustrative embodiment, each of the DNV sensors 510 can monitortheir location. For example, the DNV sensors 510 can each include a GPSsensor that determines the geographical location of the respective DNVsensor 510. In another example, the buoy 505 and/or the DNV sensors 510monitor the location of the DNV sensors 510 with respect to the buoy505. For example, the direction that each DNV sensor 510 is from thebuoy 505, the distance that each DNV sensor 510 is from the buoy 505,and/or the depth that each DNV sensor 510 is under the surface of thewater 545 can be monitored.

In some illustrative embodiments, each of the DNV sensors 510 take avector measurement of a magnetic field such as the earth's magneticfield. Each vector measurement includes an angular component and amagnitude. In some illustrative embodiments, each of the DNV sensors 510takes a measurement of the magnetic field simultaneously. Each of theDNV sensors 510 transmit the measurement of the magnetic field to thebuoy 505. The buoy 505 can store the multiple measurements together,such as a set. In illustrative embodiments, the buoy 505 stores themeasurements locally on a storage device of the buoy 505. In analternative embodiment, the buoy 505 causes the measurements to bestored remotely, such as on a remote server. For example, the buoy 505can transmit the measurements wirelessly to a remote server or database.

In some illustrative embodiments, each of the DNV sensors 510 takemultiple measurements over time. For example, the buoy 505 receives afirst set of measurements from the DNV sensors 510, then a second set ofmeasurements, etc. The first set of measurements can be compared to thesecond set of measurements. If there is a difference between the firstset and the second set of measurements, then it can be determined that amagnetic object 525 may be nearby.

As mentioned above, the earth's magnetic field and/or the backgroundmagnetic field can change over time. Thus, in some instances, there arerelatively minor differences between the first set of measurements andthe second set of measurements because of the change in the earth'smagnetic field. Accordingly, in an some illustrative embodiments, it maybe determined that the magnetic object 325 is nearby if the differencesbetween the first set of measurements and the second set of measurementsis larger than a threshold amount. The threshold amount can be largeenough that changes from the first set to the second set caused by thechanges in the earth's magnetic field are ignored, but is small enoughthat changes caused by movement of the magnetic object 525 are largerthan the threshold amount.

In some illustrative embodiments, the first set of measurements may becompared to the second set of measurements by comparing the measurementsfrom respective DNV sensors 510. For example, the measurement form afirst DNV sensor 510 in the first set may be compared to the measurementfrom the first DNV sensor 510 in the second set. In some illustrativeembodiments, if the difference from the first set to the second set fromany one of the DNV sensors 510 is above a threshold amount (e.g., thedirection and/or the magnitude), then it is determined that the magneticobject 525 is nearby. In an alternative embodiment, the differences fromeach of the DNV sensors 510 are combined and if the combined differencesare greater than the threshold amount, then it is determined that themagnetic object 525 is present.

For example, the DNV sensors 510 each take a measurement of the magneticfield once per second. The buoy 505 receives each of the measurementsand stores them as sets of measurements. The most recently received setof measurements is compared to the previously received set ofmeasurements. As the magnetic object 525 moves closer or moves aroundwhen in detection range, the magnetic object 525 disrupts the magneticfield. The DNV sensors 510 may be distributed around the buoy 505 andthe magnetic field at the points detected by the DNV sensors 510 may beaffected differently based on the location of the magnetic object 525.In an alternative embodiment, the vector measurements from each set arecompared to one another, similar to the method described with respect toFIGS. 3 and 4.

In an illustrative embodiment, the size and/or location of the magneticobject 525 can be determined based on the changes from one set ofmeasurements to another. For example, DNV sensors 510 can each send itslocation and the magnetic measurement. It can be determined that the DNVsensor 510 with the largest change in measurement is closest to themagnetic object 525. The amount of change in the DNV sensors 510 aroundthe DNV sensor 510 with the largest change in measurement can be used todetermine the direction of movement and the location of the magneticobject 525. For example, if the rate of change is increasing away from abaseline amount for a DNV sensor 510, it can be determined that themagnetic object 525 is approaching the DNV sensor 510.

FIG. 6 is a diagram of an aerial DNV sensor array in accordance with anillustrative embodiment. An illustrative system 600 includes unmannedaerial systems (UASs), a magnetic object 625, and a central processingunit 635. In an illustrative embodiment, one DNV sensor is mounted toeach UAS 610. In an alternative embodiment, each UAS 610 has multipleDNV sensors mounted thereto. In alternative embodiments, additional,fewer, and/or different elements may be used. For example, althoughthree UASs 610 are shown in FIG. 6, alternative embodiments may use two,four, five, six, ten, twenty, one hundred, etc. UASs 610.

In an illustrative embodiment, inertial stabilization and/orcompensation can be used for the DNV sensors on the UASs 610. Forexample, one or more gyroscopic inertial stabilization systems can beused to reduce the vibration and/or to compensate for the movement ofthe UAS 610. For example, the UAS 610 may lean to the right with respectto the earth, but the inertial stabilization system can cause the DNVsensor to remain parallel (or in any other suitable position) withrespect to the earth.

In an illustrative embodiment, an inertial compensation system can beused on the UASs 610. For example, a sensor can monitor the vibrationand/or position of the body of the UAS 610. The DNV sensor can besecurely attached to the body of the UAS 610. The sensed vibrationand/or position of the body can be used to augment the vector readingfrom the DNV sensor. For example, a first DNV vector measurement may betaken when the UAS 610 is parallel to the earth. A second DNV sensorvector measurement may be taken with the UAS 610 is leaning to the rightwith respect to the earth. The inertial compensation system can adjustthe vector measurement of the second DNV sensor measurement such thatthe measurement is as if the UAS 610 was parallel with respect to theearth. For example, the a compensation angle can be added to the anglecomponent of the vector measurement.

In an illustrative embodiment, the UASs 610 can be used to detect andlocate the magnetic object 625. The magnetic object 625 can be anysuitable paramagnetic or ferromagnetic object or any suitable devicethat generates a magnetic field, such as a ship, a boat, a submarine, adrone, an airplane, a torpedo, a missile, a tank, a truck, a car, landmines, underwater mines, railroad tracks, pipelines, electrical lines,etc.

In some illustrative embodiments, the earth's magnetic field of an areacan be mapped and stored in a database, such as at the centralprocessing unit 635. For example, the UASs 610 can fly around the areaand each take multiple magnetometer readings across the area todetermine a baseline magnetic field of the area. In some illustrativeembodiments, once a baseline map of the area has been determined, theUASs 610 can monitor the area for changes from the baseline map. Forexample, after a baseline map is generated, a second map of the area canbe generated. In some illustrative embodiments, the baseline map and thesecond map include measurement locations that are the same. The baselinemap and the second map can be compared to one another. If there has beenmovement from a magnetic object (e.g., the magnetic object 625), thenthe baseline map and the second map will have differences. If there isno movement from the magnetic object 625, then the baseline map and thesecond map will be largely the same.

As noted above, a measurement of the earth's magnetic field can includeinterference from various sources and/or changes over time. However, insome instances, the changes over time are gradual and relatively slow.Thus, in some illustrative embodiments, the baseline map and the secondmap can be generated relatively close in time to one another. That is,the closer that the baseline map and the second map are generated, thedifferences from the baseline map and the second map will be caused morefrom the magnetic object 625 rather than changes in the earth's magneticfield. To put it another way, common mode rejection or moving targetindication processing can be used to determine that the magnetic object625 is moving.

However, in some embodiments, the interference or noise can be removedfrom the measurements of the UASs 610. That is, the measurements fromthe UASs 610 can be taken simultaneously (e.g., be time-aligned). Thus,the measurements from each of the UASs 610 are affected the same fromthe interference sources (e.g., the sun). Any suitable common-moderejection techniques can be used, such as using Fourier transforms(e.g., fast-Fourier transforms (FFT)) or other frequency-domain methodsfor identifying and removing frequencies that are not consistent overtime (e.g., not the earth's magnetic field frequency). In someinstances, the multiple measurements can be subtracted from one anotherin the time domain to identify (and remove) the noise.

In some embodiments, noise in the various measurements will cancelstatistically because the noise is uncorrelated. Thus, comparing abaseline map to additional vector measurements (e.g., a second map),motion of the magnetic object 625 can be detected. By analyzing thechanges in the magnetic field, the direction of movement of the magneticobject 625 can be determined. Similarly, based on the changes in thedetected earth's magnetic field, additional details of the magneticobject 625 can be determined. For example, the size and/or dimensions ofthe magnetic object 625 can be determined. In some instances, based onthe changes in the earth's magnetic field, the magnetic object 625 canbe classified as a type of a magnetic object (e.g., a vehicle, agenerator, a motor, a submarine, a boat, etc.).

In some embodiments, the earth's magnetic lines will form distinctpatterns around metallic and/or magnetic objects. Such patterns can bemapped (e.g., using the UASs 610) and compared to previously-determinedpatterns corresponding to known objects to determine what the object is.Such a technique may be used regardless of whether the object is moving.For example, for a large object such as a submarine, a single mapping ofthe earth's magnetic field may be used to determine that the object is asubmarine based on the pattern of the earth's magnetic field lines.

In such an example, it may also be determined that the disturbances inthe earth's magnetic field lines are caused by an object of interest(e.g., the submarine) because no other metallic objects are around(e.g., there are no steel buildings in the middle of the ocean).

In some embodiments, the UASs 610 fly around the area that waspreviously mapped. Each of the UASs 610 transmits their measurement andlocation to the central processing unit 635. The UASs 610 can determinetheir location using any suitable method, such as GPS, celestial orstellar navigation, radio or LORAN navigation, etc. The location of theUASs 610 can include a coordinate (e.g., latitude and longitude) and anelevation. In such embodiments, the location of the UASs 610 can be athree-dimensional location. In an illustrative embodiment, the centralprocessing unit 635 can determine the location of each of the UASs 610.For example, each of the UASs 610 can transmit a message at the sametime. Based on the time that the message reaches the central processingunit 635 (e.g., the travel time of the message) and the direction fromwhich the message was received, the central processing unit 635 candetermine the location of each of the UASs 610. In alternativeembodiments, any suitable method of monitoring the location of the UASs610 can be used.

In some embodiments, the central processing unit 635 can compare thereceived measurement from each of the UASs 610 with the magnetic fieldof the baseline map corresponding to the location of the respective UAS610. For example, the central processing unit 635 can receive ameasurement and a location from a UAS 610. The central processing unit635 can determine or look up an expected magnetic field measurementbased on the location of the UAS 610 and the previously-determinedmagnetic field map. If the difference between the expected measurementand the received measurement is above a threshold amount, it can bedetermined that the magnetic object 625 is not within the monitoredarea.

In some instances, the magnetic object 625 creates a magnetic field. Forexample, engines or motors can create magnetic fields. In someembodiments, the magnetic object 625 is a direct-current motor thatcreates a magnetic field. In some embodiments, the magnetic field of themagnetic object 625 can be detected by the UASs 610.

In some illustrative embodiments, the magnetic object 625 creates amagnetic field that is detected by two or more of the UASs 610. Forexample, the previously-determined magnetic map of the area can be usedto subtract the earth's magnetic field (or any other background magneticfield) from the measurement, thereby leaving the magnetic fieldgenerated by the magnetic object 625. For example, the expected magneticmeasurement is a vector measurement determined from a pre-determined mapand the location of the UAS 610. The measurement from the UAS 610 isalso a vector. The pre-determined vector measurement can be subtractedfrom the vector measurement of the UAS 610. The resultant vector can beused to determine the location of the magnetic object 625. For example,the vector direction from the location of the UAS 610 can be used todetermine the location of the magnetic object 625 by determining theintersection of the earth's surface and the vector direction. In such anexample, it is assumed that the magnetic object 625 is on the surface ofthe earth's surface.

In some illustrative embodiments, the magnetic object 625 creates aunique magnetic field that can be used to determine what the magneticobject 625 is. For example, a direct current motor may have a magneticsignature that is different than an automobile engine. The magneticfield of the magnetic object 625 can be detected and the magneticsignature of the magnetic object 625 can be used to identify themagnetic object 625. In some embodiments, the magnetic field of themagnetic object 625 is distinguished from the earth's magnetic field(e.g., by subtraction of a baseline map and a second map).

In another example, the magnetic field from the magnetic object 625 canbe measured from two (or more) UASs 610. Di-lateration (ormultilateration) can be used to determine the location of the magneticobject 625. For example, based on the determined vector of the magneticobject from the location of each of the UASs 610, the location of themagnetic object 625 can be determined to be the intersection of thevector directions.

In some illustrative embodiments, the system 600 can be used to maplarge magnetic objects. For example, oil fields have subterranean oilspread over large areas. Like the earth's oceans, the oil in the oilfields are affected by tides. That is, the body of oil flows from oneend of the oil field to the other. Thus, the depth of the oil fieldchanges throughout a day based on the tidal flow of the oil.Accordingly, the effect on the earth's magnetic field sensed aboveground over the oil field changes throughout the day based on the tidalflow of the oil. In an illustrative embodiment, the UASs 610 can flyaround an area and monitor the change in the sensed earth's magneticfield. For areas above the oil field with oil, the earth's magneticfield as sensed by the UASs 610 will fluctuate on a cycle that issimilar to the tidal cycle of the oceans. For areas that are not abovethe oil, the earth's magnetic field will not be affected on a tidalcycle. Accordingly, by monitoring the sensed earth's magnetic field overa period of time such as 12 hours, 24 hours, 36 hours, two days, threedays, a week, etc. over an area, it can be determined where the oilfield is (e.g., where the oil is) by determining which areas have tidalchanges in the sensed earth's magnetic field.

Although FIG. 6 illustrates the UASs 610 as aerial devices, any othersuitable dirigible or device may be used. For example, DNV sensors maybe attached to autonomous cars or other terrestrial vehicles. In anotherexample, DNV sensors may be attached to autonomous ships or submarines.In alternative embodiments, the devices may not be autonomous but may beremotely controlled (e.g., by the central processing unit). In yet otherembodiments, the devices may controlled in any suitable fashion, such asvia an onboard pilot. Embodiments of the teachings described herein neednot be limited to certain types of vehicles.

FIG. 7 is a flow chart of a method for monitoring for magnetic objectsin accordance with an illustrative embodiment. In alternativeembodiments, additional, fewer, and/or different elements may be used.Also, the used of a flow chart and/or arrows is not meant to be limitingwith respect to the order of operations or flow of information. Forexample, in some embodiments, two or more operations may be performedsimultaneously.

In an operation 705, first magnetic readings of an area to be monitoredare received. For example, the UASs 610 can fly around the area to bemonitored. Each of the UASs 610 can take a magnetic measurement using,for example, a DNV sensor, and the UASs 610 can transmit to the centralprocessing unit 635 the magnetic reading and the location of therespective UAS 610 when the reading was taken. In an operation 710, thefirst magnetic readings received in the operation 705 is used togenerate a baseline map of the area. For example, each of themeasurements can be stored in connection with the three-dimensionallocation. In some instances the individual measurements can be averagedover the space to create the baseline map.

In an operation 720, second magnetic readings of the area are received.For example, the UASs 610 can fly around the area and monitor themagnetic field of the area. The measured magnetic field and the locationof the respective UAS 610 can be transmitted to the central processingunit 635. In an operation 725, the second magnetic readings are comparedto the baseline map. For example, a measurement received from a UAS 610and the measurement is compared to a measurement from the baseline mapcorresponding to the location of the UAS 610.

In an operation 730, it is determined whether differences between thesecond magnetic readings and the baseline map are greater than athreshold amount. In an illustrative embodiment, if the receiveddifferences in either the magnitude or the direction of the secondmagnetic readings and the baseline map are greater than a thresholdamount, then it is determined in an operation 735 that there is amagnetic object in the area. If not, then in the operation 745, it isdetermined that there is not a magnetic object in the area.

In an operation 740, the location of the magnetic object is determined.In an illustrative embodiment, the difference in the direction from twoor more UAS 610 measurements and the direction of the stored baselinemap can be used to determine the location of the magnetic object. Anysuitable technique for determining the location of the magnetic objectcan be used, such as di-lateration, multilateration, triangulation, etc.

FIG. 8 is a block diagram of a computing device in accordance with anillustrative embodiment. An illustrative computing device 800 includes amemory 805, a processor 810, a transceiver 815, a user interface 820,and a power source 825. In alternative embodiments, additional, fewer,and/or different elements may be used. The computing device 800 can beany suitable device described herein. For example, the computing device800 can be a desktop computer, a laptop computer, a smartphone, aspecialized computing device, etc. The computing device 800 can be usedto implement one or more of the methods described herein.

In an illustrative embodiment, the memory 805 is an electronic holdingplace or storage for information so that the information can be accessedby the processor 810. The memory 805 can include, but is not limited to,any type of random access memory (RAM), any type of read only memory(ROM), any type of flash memory, etc. such as magnetic storage devices(e.g., hard disk, floppy disk, magnetic strips, etc.), optical disks(e.g., compact disk (CD), digital versatile disk (DVD), etc.), smartcards, flash memory devices, etc. The computing device 800 may have oneor more computer-readable media that use the same or a different memorymedia technology. The computing device 800 may have one or more drivesthat support the loading of a memory medium such as a CD, a DVD, a flashmemory card, etc.

In an illustrative embodiment, the processor 810 executes instructions.The instructions may be carried out by a special purpose computer, logiccircuits, or hardware circuits. The processor 810 may be implemented inhardware, firmware, software, or any combination thereof. The term“execution” is, for example, the process of running an application orthe carrying out of the operation called for by an instruction. Theinstructions may be written using one or more programming language,scripting language, assembly language, etc. The processor 810 executesan instruction, meaning that it performs the operations called for bythat instruction. The processor 810 operably couples with the userinterface 820, the transceiver 815, the memory 805, etc. to receive, tosend, and to process information and to control the operations of thecomputing device 800. The processor 810 may retrieve a set ofinstructions from a permanent memory device such as a ROM device andcopy the instructions in an executable form to a temporary memory devicethat is generally some form of RAM. An illustrative computing device 800may include a plurality of processors that use the same or a differentprocessing technology. In an illustrative embodiment, the instructionsmay be stored in memory 805.

In an illustrative embodiment, the transceiver 815 is configured toreceive and/or transmit information. In some embodiments, thetransceiver 815 communicates information via a wired connection, such asan Ethernet connection, one or more twisted pair wires, coaxial cables,fiber optic cables, etc. In some embodiments, the transceiver 815communicates information via a wireless connection using microwaves,infrared waves, radio waves, spread spectrum technologies, satellites,etc. The transceiver 815 can be configured to communicate with anotherdevice using cellular networks, local area networks, wide area networks,the Internet, etc. In some embodiments, one or more of the elements ofthe computing device 800 communicate via wired or wirelesscommunications. In some embodiments, the transceiver 815 provides aninterface for presenting information from the computing device 800 toexternal systems, users, or memory. For example, the transceiver 815 mayinclude an interface to a display, a printer, a speaker, etc. In anillustrative embodiment, the transceiver 815 may also includealarm/indicator lights, a network interface, a disk drive, a computermemory device, etc. In an illustrative embodiment, the transceiver 815can receive information from external systems, users, memory, etc.

In an illustrative embodiment, the user interface 820 is configured toreceive and/or provide information from/to a user. The user interface820 can be any suitable user interface. The user interface 820 can be aninterface for receiving user input and/or machine instructions for entryinto the computing device 800. The user interface 820 may use variousinput technologies including, but not limited to, a keyboard, a stylusand/or touch screen, a mouse, a track ball, a keypad, a microphone,voice recognition, motion recognition, disk drives, remote controllers,input ports, one or more buttons, dials, joysticks, etc. to allow anexternal source, such as a user, to enter information into the computingdevice 800. The user interface 820 can be used to navigate menus, adjustoptions, adjust settings, adjust display, etc.

The user interface 820 can be configured to provide an interface forpresenting information from the computing device 800 to externalsystems, users, memory, etc. For example, the user interface 820 caninclude an interface for a display, a printer, a speaker,alarm/indicator lights, a network interface, a disk drive, a computermemory device, etc. The user interface 820 can include a color display,a cathode-ray tube (CRT), a liquid crystal display (LCD), a plasmadisplay, an organic light-emitting diode (OLED) display, etc.

In an illustrative embodiment, the power source 825 is configured toprovide electrical power to one or more elements of the computing device800. In some embodiments, the power source 825 includes an alternatingpower source, such as available line voltage (e.g., 120 Voltsalternating current at 60 Hertz in the United States). The power source825 can include one or more transformers, rectifiers, etc. to convertelectrical power into power useable by the one or more elements of thecomputing device 800, such as 1.5 Volts, 8 Volts, 12 Volts, 24 Volts,etc. The power source 825 can include one or more batteries.

In an illustrative embodiment, any of the operations described hereincan be implemented at least in part as computer-readable instructionsstored on a computer-readable memory. Upon execution of thecomputer-readable instructions by a processor, the computer-readableinstructions can cause a node to perform the operations.

The herein described subject matter sometimes illustrates differentcomponents contained within, or connected with, different othercomponents. It is to be understood that such depicted architectures aremerely exemplary, and that in fact many other architectures can beimplemented which achieve the same functionality. In a conceptual sense,any arrangement of components to achieve the same functionality iseffectively “associated” such that the desired functionality isachieved. Hence, any two components herein combined to achieve aparticular functionality can be seen as “associated with” each othersuch that the desired functionality is achieved, irrespective ofarchitectures or intermedial components. Likewise, any two components soassociated can also be viewed as being “operably connected,” or“operably coupled,” to each other to achieve the desired functionality,and any two components capable of being so associated can also be viewedas being “operably couplable,” to each other to achieve the desiredfunctionality. Specific examples of operably couplable include but arenot limited to physically mateable and/or physically interactingcomponents and/or wirelessly interactable and/or wirelessly interactingcomponents and/or logically interacting and/or logically interactablecomponents.

With respect to the use of substantially any plural and/or singularterms herein, those having skill in the art can translate from theplural to the singular and/or from the singular to the plural as isappropriate to the context and/or application. The varioussingular/plural permutations may be expressly set forth herein for sakeof clarity.

It will be understood by those within the art that, in general, termsused herein, and especially in the appended claims (e.g., bodies of theappended claims) are generally intended as “open” terms (e.g., the term“including” should be interpreted as “including but not limited to,” theterm “having” should be interpreted as “having at least,” the term“includes” should be interpreted as “includes but is not limited to,”etc.). It will be further understood by those within the art that if aspecific number of an introduced claim recitation is intended, such anintent will be explicitly recited in the claim, and in the absence ofsuch recitation no such intent is present. For example, as an aid tounderstanding, the following appended claims may contain usage of theintroductory phrases “at least one” and “one or more” to introduce claimrecitations. However, the use of such phrases should not be construed toimply that the introduction of a claim recitation by the indefinitearticles “a” or “an” limits any particular claim containing suchintroduced claim recitation to inventions containing only one suchrecitation, even when the same claim includes the introductory phrases“one or more” or “at least one” and indefinite articles such as “a” or“an” (e.g., “a” and/or “an” should typically be interpreted to mean “atleast one” or “one or more”); the same holds true for the use ofdefinite articles used to introduce claim recitations. In addition, evenif a specific number of an introduced claim recitation is explicitlyrecited, those skilled in the art will recognize that such recitationshould typically be interpreted to mean at least the recited number(e.g., the bare recitation of “two recitations,” without othermodifiers, typically means at least two recitations, or two or morerecitations). Furthermore, in those instances where a conventionanalogous to “at least one of A, B, and C, etc.” is used, in generalsuch a construction is intended in the sense one having skill in the artwould understand the convention (e.g., “a system having at least one ofA, B, and C” would include but not be limited to systems that have Aalone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). In those instances where aconvention analogous to “at least one of A, B, or C, etc.” is used, ingeneral such a construction is intended in the sense one having skill inthe art would understand the convention (e.g., “a system having at leastone of A, B, or C” would include but not be limited to systems that haveA alone, B alone, C alone, A and B together, A and C together, B and Ctogether, and/or A, B, and C together, etc.). It will be furtherunderstood by those within the art that virtually any disjunctive wordand/or phrase presenting two or more alternative terms, whether in thedescription, claims, or drawings, should be understood to contemplatethe possibilities of including one of the terms, either of the terms, orboth terms. For example, the phrase “A or B” will be understood toinclude the possibilities of “A” or “B” or “A and B.” Further, unlessotherwise noted, the use of the words “approximate,” “about,” “around,”“substantially,” etc., mean plus or minus ten percent.

The foregoing description of illustrative embodiments has been presentedfor purposes of illustration and of description. It is not intended tobe exhaustive or limiting with respect to the precise form disclosed,and modifications and variations are possible in light of the aboveteachings or may be acquired from practice of the disclosed embodiments.It is intended that the scope of the invention be defined by the claimsappended hereto and their equivalents.

What is claimed is:
 1. A system comprising: a plurality of magnetometersthat are each configured to generate a vector measurement of a magneticfield; a central processing unit that is communicatively coupled to eachof the magnetometers, wherein the central processing unit is configuredto: receive, from each of the plurality of magnetometers, the respectivevector measurement of the magnetic field; compare each of the vectormeasurements to determine differences in the vector measurements;determine, based on the differences in the vector measurements, that amagnetic object is near the plurality of magnetometers.
 2. The system ofclaim 1, further comprising a tether, wherein each of the plurality ofmagnetometers are attached along the tether.
 3. The system of claim 2,further comprising a weight attached to a first end of the tether,wherein a housing of the central processing unit is attached to a secondend of the tether.
 4. The system of claim 2, wherein the plurality ofmagnetometers are suspended at different depths in water.
 5. The systemof claim 2, wherein the magnetometers communicate with the centralprocessing unit via the tether.
 6. The system of claim 1, furthercomprising a plurality of tethers, wherein each of the plurality ofmagnetometers are fixed to a respective one of the plurality of tethers.7. The system of claim 1, wherein the magnetometers are diamondsnitrogen-vacancy (DNV) sensors.
 8. The system of claim 1, furthercomprising a buoy, wherein the central processing unit is located withinthe buoy.
 9. The system of claim 1, further comprising a buoy, whereineach of the magnetometers are attached to the buoy via one or moretethers, and wherein the central processing unit is remote from thebuoy.
 10. The system of claim 9, wherein the buoy transmits the vectormeasurements from to the central processing unit wirelessly.
 11. Thesystem of claim 1, wherein the central processing unit is furtherconfigured to determine a location of the magnetic object based on thedifferences in the vector measurements.
 12. The system of claim 11,wherein, to determine the location of the magnetic object, the centralprocessing unit is configured to compare the differences in the vectormeasurements to a database of previously determined locations andcorresponding previously-determined differences in vector measurements.13. The system of claim 11, wherein the central processing unit isfurther configured to: determine a location of each of themagnetometers; and determine a location of the magnetic field based onthe location of each of the magnetometers and the differences in thevector measurements.
 14. The system of claim 13, wherein each of theplurality of magnetometers are further configured to monitor thelocation of the respective magnetometer in relation to the a centralpoint, and wherein to determine the location of each of the plurality ofmagnetometer, the central processing unit is configured to receive thelocation of each of the plurality of magnetometers from the respectivemagnetometer.
 15. The system of claim 1, wherein the plurality ofmagnetometers are configured to generate the vector measurementssimultaneously.
 16. The system of claim 1, wherein the magnetic field isnot generated by a device.
 17. The system of claim 1, wherein themagnetic field is the earth's magnetic field.
 18. A method comprising:receiving, from each of a plurality of magnetometers, a respectivevector measurement of a magnetic field; comparing each of the vectormeasurements to determine differences in the vector measurements;determining, based on the differences in the vector measurements, that amagnetic object is near the plurality of magnetometers.
 19. The methodof claim 18, further comprising determining a location of the magneticobject based on the differences in the vector measurements.
 20. Themethod of claim 18, further comprising: determining a location of eachof the magnetometers; and determining a location of the magnetic fieldbased on the location of each of the magnetometers and the differencesin the vector measurements.